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2016, 8 (3) Online: 01 June 2016 Previous issue Next issue
  • Identification, characteristics and classification of cryogenic block streams
  • Stuart A. Harris
  • DOI: 10.3724/SP.J.1226.2016.00177
  • 2016, Vol.8 (3): 177–186 Abstract ( 31) HTML PDF (2293 KB) ( 21 )
  • Cryogenic block streams consist of a stream of rocks superficially resembling a stream deposit but lacking a matrix,usually occurring on a valley or gully floor or on slopes that are less steep than the maximum angle of repose of coarse sediments.They are usually formed on perennially frozen ground,but can also occur as relict landforms.There are three main active kinds forming today,viz.,Siberian and Tibetan dynamic rock streams and lag block streams.During their formation,the blocks in the active Siberian and Tibetan dynamic block streams move downslope at up to 1 m/a.They are forming today on the Tibetan Plateau and in the more arid parts of south-central Siberia,although the processes involved in the movement are different.In the case of the Tibetan type,individual blocks slide downslope over the substrate in winter on an icy coating in areas of minimal winter precipitation.The Siberian type develops in areas of 15-80 cm of winter snow cover and an MAAT (mean annual air temperature) of -4℃ to -17℃.The movement is due to creep of snow and ice and collapse of the blocks downslope during thawing.Lag block streams are formed by meltwater flowing over the surface of sediment consisting primarily of larger blocks with a limited amount of interstitial sediment.The erosion of the matrix is primarily in the spring in areas of higher winter precipitation on 10°-30° slopes.The blocks remain stationary,but the interstitial sediment is washed out by strong seasonal flows of meltwater or rain to form an alluvial fan.The boulders undergo weathering and become more rounded in the process.Lag block streams can also develop without the presence of permafrost in areas with cold climates or glaciers.Block streams also occur as relict deposits in older deposits under various climatic regimes that are unsuitable for their formation today.An example of relict lag block streams with subangular to subrounded blocks occurs in gullies on the forested mountainsides at Felsen in Germany,and is the original "felsenmeer".Similar examples occur near Vitosha Mountain in Bulgaria.The"stone runs"in the Falkland Islands are examples of the more angular relict lag block streams.In both Tasmania and the Falkland Islands,they mask a more complex history,the underlying soils indicating periods of tropical and temperate soil formation resulting from weathering during and since the Tertiary Period.Block streams have also been reported from beneath cold-based glaciers in Sweden,and below till in Canada,and when exhumed,can continue to develop.
  • Wind tunnel simulation of the effects of freeze-thaw cycles on soil erosion in the Qinghai-Tibet Plateau
  • ShengBo Xie, JianJun Qu, Tao Wang
  • DOI: 10.3724/SP.J.1226.2016.00187
  • 2016, Vol.8 (3): 187–195 Abstract ( 39) HTML PDF (4869 KB) ( 28 )
  • Intense freezing and thawing actions occur in the Qinghai-Tibet Plateau because of its high elevation and cold temperature.The plateau's unique environment makes it easy to generate wind erosion under dry,windy weather conditions,resulting in the emergence of desertification.As a major form of freeze-thaw erosion,freeze-thaw and wind erosion is displayed prominently on the Qinghai-Tibet Plateau.Therefore,in this study,soil samples were collected from the surface of the plateau to undergo freeze-thaw and wind erosion simulation experiments.Results show that wind erosion strength increases with an increasing number of freeze-thaw cycles,water content in the freezing-thawing process,and the difference in freeze-thaw temperatures.Therefore,in the conditions of water participation,the main reason for the freeze-thaw and wind erosion in the Qinghai-Tibet Plateau is the damage to the soil structure by repeated,fierce freeze-thaw actions,and the sand-bearing wind is the main driving force for this process.The research results have theoretical significance for exploring the formation mechanism of freeze-thaw and wind erosion in the Qinghai-Tibet Plateau,and provide a scientific basis for freeze-thaw desertification control in the plateau.
  • The adaptive significance of differences of root morphology, anatomy and physiology from three ecotypes of reed (Phragmites communis Trin.)
  • YuBing Liu, XinRong Li, ZhiShan Zhang, XiaoJun Li, Jin Wang
  • DOI: 10.3724/SP.J.1226.2016.00196
  • 2016, Vol.8 (3): 196–204 Abstract ( 35) HTML PDF (769 KB) ( 19 )
  • Reeds are widely distributed in drought and high salt conditions of northwestern China.Leaf epidermal micromorphology,anatomy,chloroplast ultrastructure and physio-chemical characteristics due to long-term adaptation in the natural habitats of common reed (Phragmites communis Trin.) contrasted considerably among three different ecotypes:dune reed (DR),Gobi salt reed (GSR) and swamp reed (SR).The main objective of the present study is to determine the adapting characteristics of morphology,anatomy and physiological responses of thin roots in DR,GSR and SR.The results show that root length density was higher in SR and few root hairs were observed in DR.Cross-section anatomical features show that each ecotype has an endodermis and exodermis,while cortex thickness and proportion of root cortical aerenchyma and stele in root structure varied among the three ecotypes.The stele and xylem share a larger area in DR compared to GSR and SR.GSR has a large proportion of the cortex with radialized distribution of aerenchyma cells spacing,and the cortex has a peripheral,mechanically stiff ring in the exodermis.SEM and TEM microscope images show that GSR has a sclerenchyma ring with high lignification in the exodermis.The physio-chemical parameters show that GSR had a higher level of stress tolerance than DR.These findings indicate that developed water-absorbing tissues were largely distributed in the root structure of DR,and a main framework with supporting function spacing with aerenchyma was dominant in GSR in the long term adaptation to their natural habitats,respectively.
  • Proline and soluble sugars accumulation in three pepper species (Capsicum spp) in response to water stress imposed at different stages of growth
  • Gideon O. Okunlola, Richard O. Akinwale, Adekunle A. Adelusi
  • DOI: 10.3724/SP.J.1226.2016.00205
  • 2016, Vol.8 (3): 205–211 Abstract ( 40) HTML PDF (325 KB) ( 31 )
  • Drought is a major production constraint for major fruits and vegetable crops in the tropics.This study was conducted to investigate the effect of limited water supply at three growth stages (vegetative,flowering and fruiting) on the accumulation of proline and soluble sugars in three pepper species.Seeds of the three pepper species,Capsicum chinense Jacq.,C.annuum L.and C.frutescens L.were raised in a nursery and the seedlings were transplanted into seventy two plastic pots arranged in a randomized complete block design with three replicates,25 days after planting.Four water treatments,200 mL of water supplied twice daily (W1),once in every three days (W2),once in every five days (W3),and zero water supplied throughout growing period (W0) were imposed at three vegetative,flowering,and fruiting growth stages.Data were collected on relative water content,free proline and total soluble sugar.Data collected were subjected to analysis of variance and means were separated using Duncan's multiple range test.Results show that the concentration of proline and soluble sugar in leaves of the three pepper species were found to be remarkable at the different stages of growth in the stressed plants.
  • Temperature and precipitation changes in Extensive Hexi Region, China, 1960-2011
  • Wei Liu, ZongXing Li, Meng Zhu, XiaoYan Guo, LiJuan Chen
  • DOI: 10.3724/SP.J.1226.2016.00212
  • 2016, Vol.8 (3): 212–226 Abstract ( 32) HTML PDF (633 KB) ( 15 )
  • Global climate change has been evident in many places worldwide.This study provides a better understanding of the variability and changes in frequency,intensity,and duration of temperature,precipitation,and climate extremes in the Extensive Hexi Region,based on meteorological data from 26 stations.The analysis of average,maximum,and minimum temperatures revealed that statistically significant warming occurred from 1960 to 2011.All temperature extremes displayed trends consistent with warming,with the exception of coldest-night temperature (TNn) and coldest-day temperature (TXn),which were particularly evident in high-altitude areas and at night.Amount of precipitation and number of rainy days slowly increased with no significant regional trends,mainly occurring in the Qilian Mountains and Hexi Corridor.The significance of changes in precipitation extremes during 1960-2011 was high,but the regional trends of maximum 5-day precipitation (RX5day),the average precipitation on wet days (SDⅡ),and consecutive wet days (CWD) were not significant.The variations in the studied parameters indicate an increase in both the extremity and strength of precipitation events,particularly in higher-altitude regions.Furthermore,the contribution from very wet precipitation (R95) and extremely wet precipitation (R99) to total precipitation also increased between 1960 and 2011.The assessment of these changes in temperature and precipitation may help in developing better management practices for water resources.Future studies in the region should focus on the impact of these changes on runoffs and glaciers.
  • The impacts of climate change on hydrology in a typical glacier region-A case study in Hailuo Creek watershed of Mt.Gongga in China
  • GuoFeng Zhu, YuanQing He, DaHe Qin, HongKai Gao, Tao Pu, DongDong Chen, Kai Wang
  • DOI: 10.3724/SP.J.1226.2016.00227
  • 2016, Vol.8 (3): 227–240 Abstract ( 38) HTML PDF (3312 KB) ( 20 )
  • The glaciers of the Hengduan Mountains play an important role in the hydrology processes of this region.In this study,the HBV Light model,which relies on a degree-day model to simulate glacier melting,was employed to simulate both glacier runoff and total runoff.The daily temperature and precipitation at the Hailuo Creek No.1 Glacier from 1952 to 2009 were obtained from daily meteorological observed data at the glacier and from six national meteorological stations near the Hailuo Creek Basin.The daily air temperature,precipitation,runoff depth,and monthly potential evaporation in 1995,1996,and 2002 were used to obtain a set of optimal parameters,and the annual total runoff and glacier runoff of the Hailuo Creek Glacier (1952-2009) were calculated using the HBV Light model.Results showed the average annual runoff in the Hailuo Creek Basin was 2,114 mm from 1952 to 2009,of which glacial melting accounted for about 1,078 mm.The river runoff in the Hailuo Creek catchment increased as a result of increased glacier runoff.Glacier runoff accounted for 51.1% of the Hailuo Creek stream flow in 1994 and increased to 72.6% in 2006.About 95% of the increased stream flow derived from the increased glacier runoff.
  • Hydrological effects of alpine permafrost in the headwaters of the Urumqi River, Tianshan Mountains
  • TianDing Han, HongZheng Pu, Peng Cheng, KeQin Jiao
  • DOI: 10.3724/SP.J.1226.2016.00241
  • 2016, Vol.8 (3): 241–249 Abstract ( 30) HTML PDF (6086 KB) ( 15 )
  • Against the background of climate change,alpine permafrost active layers have shown a gradual thickening trend and the hydrothermal conditions have undergone significant changes in the Tianshan Mountains and the Qinghai-Tibet Plateau,China.At the ice-free cirque basins in the headwaters of the Urumqi River (hereafter referred to as the Ice-Free Cirque) in eastern Tianshan,China,the hydrological effects of the alpine permafrost active layers appear to have also exhibited significant changes recently.The increasing trend of local precipitation is clear in May and June.The onset of winter and spring snowmelt runoff clearly lags behind increases of air temperature,and the runoff peak appears near the beginning of the melting season,which results in the spring runoff increasing.In summer,runoff decreases strongly and the maximum runoff occurs earlier.In our analysis of meteorological and hydrologic data from 1959 to 2010,the runoff and precipitation changes are significantly correlated.In the initial stage of runoff,the runoff-producing process is mainly under the control of the soil water content and soil temperature in the 0-30 cm active layers.Spring precipitation and snowmelt water are mainly involved in the processes of infiltration and evaporation while some melt water infiltrates into the seasonal thawed layer and stays above the frozen layers.During the strong ablation period in summer,the runoff-generating process is mainly controlled by soil water content in the active layers deeper than 60 cm.In the active layer,precipitation and seasonal snowmelt water infiltrates,migrates,collects,and then forms runoff.
  • Dynamic evaluation of groundwater resources in Zhangye Basin
  • LiNa Mi, HongLang Xiao, ZhengLiang Yin, ShengChun Xiao
  • DOI: 10.3724/SP.J.1226.2016.00250
  • 2016, Vol.8 (3): 250–262 Abstract ( 30) HTML PDF (6236 KB) ( 14 )
  • Groundwater resource is vital to the sustainable development of socio-economics in arid and semi-arid regions of Northwest China.An estimation of the groundwater resources variation in Zhangye Basin was made during 1985-2013 based on long-term groundwater observation data and geostatistical method.The results show that from 1985 to 2013,groundwater storage exhibited tremendous dissimilarity on temporal and spatial scale for the whole Zhangye Basin,especially before and after implementation of the water diversion policy.Trend of groundwater storage varied from quick to slow decline or increase.The accumulative groundwater storage decreased nearly 47.52×108 m3,and annual average depletion rate reached 1.64×108 m3/a.Among which,the accumulative groundwater storage of the river and well water mixed irrigation district decreased by 37.48×108 m3,accounting for about 78.87% of the total groundwater depletion of the Zhangye Basin.Accumulative depletion of groundwater storage varied in respective irrigation districts.Though groundwater resources depletion rate slowed down from 2005,the overall storage in the whole basin and respective districts during 1985-2013 was still in a severe deficit such that,the groundwater resource was in a rather negative balance,which could threaten the local aquifer.This is the joint effect of climate change and human activities,however human activities,such as water diversion policy and groundwater exploitation,became increasingly intense.Our research results could provide a reasonable estimation for the groundwater balance in Zhangye Basin,providing a scientific basis for water resources unified planning and,this method can provide a relatively reliable way of estimation for large scale groundwater resources.
  • Classification of full-polarization ALOS-PALSAR imagery using SVM in arid area of Dunhuang
  • JunZhan Wang, JianJun Qu, WeiMin Zhang, KeCun Zhang
  • DOI: 10.3724/SP.J.1226.2016.00263
  • 2016, Vol.8 (3): 263–267 Abstract ( 33) HTML PDF (2268 KB) ( 19 )
  • Classification is an important process in interpretation of synthetic aperture radar (SAR) imagery.As an advanced instrument for remote sensing,the polarimetric SAR has been applied widely in many fields.The main aim of this paper is to explore the ability of the full-polarization SAR data in classification.The study area is a part of Dunhuang,Gansu Province,China.An L-band full-polarization image of Dunhuang which includes quad-polarization modes was acquired by the ALOS-PALSAR (Advanced Land Observing Satellite-the Phased Array type L-band Synthetic Aperture Radar).Firstly,new characteristic information was extracted by the difference operation,ratio operation,and principal component transform based on the full-polarization (HH,HV or VH,VV) modes SAR data.Then the single-,dual-,full-polarization SAR data and new SAR characteristic information were used to analyze quantitatively the classification accuracy based on the Support Vector Machines (SVM).The results show that classification overall accuracy of single-polarization SAR data is poor,and the highest is 56.53% of VV polarization.The classification overall accuracy of dual-polarization SAR is much better than single-polarization,the highest is 74.77% of HV & VV polarization data.The classification overall accuracy of full-polarization SAR is 80.21%,adding the difference characteristic information,ratio characteristic information and the first principal component (PC1) respectively,the overall accuracy increased by 3.09%,3.38%,4.14% respectively.When the full-polarization SAR data in combination with the all characteristic information,the classification overall accuracy reached to 91.01%.The full-polarization SAR data in combination with the band math characteristic information or the PC1 can greatly improve classification accuracy.